People lie. Yes, even presidents lie. Especially presidents, you might argue. And yet there’s a long history in journalism of being very, very careful about saying so.

There are excellent reasons for this standard.

Descriptions like “claimed without evidence,” “falsely said,” and “wrongly asserted” are clunky, but they also avoid explicitly describing intent. Same goes for “untruth,” “falsehood,” and “unsubstantiated claim.” Calling something a “lie” implies that the speaker knows what he said is untrue, and that he meant to deceive. (A similarly classic—and often-broken—rule in journalism is to avoid saying what someone believes. You can describe what they say they believe, the thinking goes, but there’s no way to know what someone actually believes unless you are that person.)

Questioning a sitting president’s truthfulness and actually using the words “lie,” “lied,” or “lying” has often been relegated to the opinion pages, editorials, or put in quotation marks: Let somebody else suggest the chief executive is lying about Yalta, or Cuba, or Vietnam, or trading arms for hostages, or “no new taxes,” or sexual relations with that woman, or weapons of mass destruction. This is the stuff of standard journalistic fairness.

The standard, however, is coming under pressure.

Not just by the bombastic new president of the United States and his famous tendency to exaggerate, but by that president’s embrace of new-age publishing technology—you may have heard, the guy loves to tweet—and his over-the-top disdain for journalism at a frenetic moment for the media industry.

Newsrooms have wrestled with how to characterize the misinformation Donald Trump spreads since the presidential campaign, when his eyebrow-raising statements tended more toward “pants on fire” than true, according to at least one fact-checking site. This challenge is only intensifying with Trump in the Oval Office, and backed by an administration eager to provide “alternative facts” when the actual facts don’t flatter the president.

Trump has been embroiled in so many disputes over truth that it’s difficult to know where to begin. “If falsehood, like truth, had only one face, we would be in better shape,” the philosopher Michel de Montaigne famously wrote. “But the reverse of truth has a hundred thousand shapes and a limitless field.”

So let’s start with voter fraud.

In a private meeting with Congressional leaders this week, the president doubled down on the claim—the falsehood, the untruth, the unsupported notion, the you-get-the-idea—that millions of people voted illegally in the November election, costing him the popular vote.

There is no evidence to support this extraordinary claim. But news organizations differed in how to make that clear. Here’s a sample of headlines from around the media (asterisks indicate publications that used the Associated Press story and headline):

NPR got considerable attention for its editorial judgment when it was revealed that the network “has decided not to use the word ‘lie,’” in its coverage of Trump. As soon as “you start branding things with a word like ‘lie,’ you push people away from you,” the network’s senior vice president for news told a colleague. So NPR went with this headline: “Trump Still Insists Millions Voted Illegally. (There's Still No Evidence Of That).”

The New York Times, with the blessing of the paper’s executive editor, went with a bolder framing: “Trump Repeats Lie About Popular Vote in Meeting With Lawmakers.” (Notice, though, that the paper didn’t say Trump lied; they called his claim a lie.) Dean Baquet, the paper’s top editor, told a Times reporter that “he fully understood the gravity of using the word ‘lie,’ whether in reference to an average citizen or to the president of the United States” and that he “emphasized that it should be used sparingly, partly because the term carries such negative connotations, and partly so that it does not lose potency.”

For those who pay close attention to the Times, the use of “lie” this way is indeed striking—but it isn’t surprising. During Trump’s campaign, Baquet described why the Times was comfortable referring to Trump’s conspiracy theory about Obama’s birthplace as “the birther lie” in this headline of a story published in September, after Trump finally acknowledged Obama was born in the United States: “Donald Trump Clung to ‘Birther’ Lie for Years, and Still Isn’t Apologetic.”

“I think to say that that was a ‘falsehood’ wouldn’t have captured the duration of his claim, to be frank, the outrageousness of his claim,” Baquet told NPR in an interview at the time. “I think to have called it just a falsehood would have put it in the category of, to be frank, ‘usual political fare,’ where politicians say, ‘My tax plan will save a billion dollars,’ but it’s actually a half a billion and they're using the wrong analysis. This was something else. And I think we owed it to our readers to just call it out for what it was.”

So what was it, really, when Trump claimed this week that millions of people voted illegally in November? Or when he made the same claim in a tweet late last year?

To BuzzFeed, which is keeping “A Running List Of All Of President Trump’s Lies,” it was a lie. BuzzFeed News reported that Trump “lied about voter fraud at a reception with congressional leaders” and again “lied about voter fraud on ABC News.”

In addition to winning the Electoral College in a landslide, I won the popular vote if you deduct the millions of people who voted illegally

“Clearly, he thinks it is true,” wrote one person in a letter to the Times this week, “So it’s not a lie; it’s a delusion.”

But even a delusion—one that involves blindly turning away from all evidence to the contrary—can be considered its own kind of lie. That’s what David Corn, the author of The Lies of George W. Bush, told The Atlantic in 2007: “What Bush does is that he displays a kind of willful disregard for the truth, which is the moral equivalent of lying,” Corn said, referring to then-president George W. Bush. “He doesn’t do any due diligence with the facts. Even if you believed something was true [at] the time you said it, it becomes a lie when you don’t act on new information—or correct yourself when you’ve been proven wrong.”

Corn’s description fits with Trump’s insistence on voter fraud, and with his disposition generally. Trump likes to call out others for being wrong—he relishes “wrong!” as one of the many insults he lobs in tweets—but he is not one to acknowledge his own mistakes.

He also routinely criticizes people by calling them liars. He bestowed the nickname “Lyin Ted” on his one-time political opponent Ted Cruz. And Trump has cultivated an image of brusqueness that his supporters sometimes equate with honesty—taking the idea that he isn’t afraid to say what he thinks as proof that what he says is necessarily true.

If Obama was willing to lie about ObamaCare then what else has he lied to us about…

Tweets are instructive here, both because of how they illustrate Trump’s style and as a reminder that Trump’s presidency is taking place in a media environment unlike any that preceded it. Obama is known for his social media proficiency, but Twitter was still brand new when he was first inaugurated.

No president in history has lied to the American people more than President Obama - in fact, it is not even close!

And though Trump is known to be a devoted consumer of print newspapers and cable news, people are increasingly turning to the mobile internet for information. Trump has said he sees his Twitter account as a megaphone directly to the people, and he doesn’t hesitate to scream into it. For those who pay attention to Trump’s tweeting, there’s an entire flood of people calling him a liar in his mentions—a feed that can be considered its own micro-media environment, and one that has a massive audience.

Meanwhile, in the crowded and information-rich wilds of the internet, the news cycle is as close to “real time” as technology has ever allowed it to be. “Fake news” isn’t a new concept—there was a fake news crisis in the 19th century—but the pace of the news and the scale at which hoaxes can be made and distributed is certainly a complicating factor. Traditional media gatekeepers haven’t just lost their monopoly on publishing and distribution technologies—they’ve lost institutional prestige and public trust. The loss of cultural influence among the American press benefits the Trump administration, which is clearly focused on attempts to goad reporters. “I want you to quote this,” Steve Bannon, Trump’s top White House strategist and the former chairman of Breitbart News, told The New York Times on Wednesday. “The media here is the opposition party.” Trump himself encourages the denigration of American journalism twofold: he criticizes legitimate news organizations as “fake,” and he pushes sensational claims from fringe sites.

“The pragmatic problem with official lies is their amoeba-like penchant for self-replication,” writes Eric Alterman in his book, When Presidents Lie. “The more a leader lies to his people, the more he must lie to his people.”

“Lying may appear to work for a president in the short term and, in many cases, it does,” Alterman says. “But a president ignores the consequences of his deception at his own political peril.”

If this is a problem for Trump, he seems unbothered by it. So far Trump appears far more interested in holding news organizations accountable.

With frequent dialogue among editors, reporters, and readers on social platforms, and with sites like NewsDiffs—which tracks how online articles are edited by showing side-by-side comparison of changes—scrutinizing the press is possible like never before. The internet has given news consumers a more privileged view of how journalism is produced: They can see how new information is added, the social context around corrections appended, and follow conversations about when and why headlines are tweaked. The business of news gathering is, at its core, a mission of truth seeking—and it’s a messy one. Trump, for his part, seems less interested in journalistic nuance and more concerned with coverage that offends his ego. So concerned that, in the 1980s and 1990s, he was known to call journalists and pretend to be a publicist named John “vigorously defending” Trump, as The Washington Post put it. The Post described that stunt as masquerading, not lying, for what it’s worth.

Today, the challenge of figuring out what is real—and often doing so before an audience in real time—is why journalists must be careful, as ever, with facts and words. Fairness matters. But so do accuracy and credibility. Which is why it’s just as important for journalists to call a lie “a lie” when they hear one.

Trump may have won the presidency, but he’s now fighting for his legacy. He’s also declared himself to be “in a running war with the media,” at a time when the journalism industry is in its own battle for survival. The stakes are high all around. But if journalists are up for a fight, it’s not because Trump called them “the lowest form of life,” or because his chief strategist said the news media should “keep its mouth shut.” In journalism, the fight is to hold the powerful accountable; to seek truth and report it.

President Trump seems to be banking on the idea that facts don’t matter. But presidential history, a history told first in front pages, tells us otherwise.

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Adrienne LaFrance is the editor of TheAtlantic.com. She was previously a senior editor and staff writer at The Atlantic.